Which of the following compounds will have the lowest frequency for carbonyl absorption in IR spectroscopy?

Question

Quizplus · Accepted Answer

Compound II will have the lowest frequency for carbonyl absorption in IR spectroscopy because it has a nonpolar group (methyl group) attached to the carbonyl carbon, which will decrease the dipole moment and result in a weaker infrared absorption. This is known as the steric effect. Compounds I, III, and IV have polar groups attached to the carbonyl carbon, which will increase the dipole moment and result in stronger infrared absorptions at higher frequencies.

Which of the Following Compounds Will Have the Lowest Frequency